Deficiencies in epidemiological studies of particulate air pollution and respiratory health have limited their usefulness in setting ambient air quality standards. Since only inhalable particles can cause respiratory illness, one such deficiency has been the lack of studies relating particle size distribution and particle composition to respiratory health outcomes. Pulp mill communities experience air pollution primarily of the particulate type, with coastal pulp mill communities experiencing an additional exposure from the submicronic fraction of particulates due to the fine sodium chloride (NaC1) particles resulting from hog fuel burning. The hypothesis to be tested in this study is that the observed levels of ambient particulates, especially particulates in the fine respirable fraction, are associated with adverse respiratory health effects. Ambient long-term and peak particulate exposure in the British Columbia coastal pulp mill community of Port Alberni will be estimated from a network of particulate monitors and particle counters, measuring particulate and NaC1 levels for several respirable size ranges. Three health outcomes will be evaluated: 1) prevalence of respiratory symptoms and levels of pulmonary function in approximately 2,000 elementary school aged children, 2) hospitalization due to acute bronchitis, bronchiolitis and pneumonia in children four years of age or less to be studied using a case-control design, and 3) time series of respiratory illnesses and daily level of pulmonary function in an adult population working outdoors. Because Port Alberni experiences particulate pollution over a wide range of particle sizes, this community offers a good opportunity for testing the hypothesis outlined.